12 research outputs found
Chiral tunneling and the Klein paradox in graphene
The so-called Klein paradox - unimpeded penetration of relativistic particles
through high and wide potential barriers - is one of the most exotic and
counterintuitive consequences of quantum electrodynamics (QED). The phenomenon
is discussed in many contexts in particle, nuclear and astro- physics but
direct tests of the Klein paradox using elementary particles have so far proved
impossible. Here we show that the effect can be tested in a conceptually simple
condensed-matter experiment by using electrostatic barriers in single- and
bi-layer graphene. Due to the chiral nature of their quasiparticles, quantum
tunneling in these materials becomes highly anisotropic, qualitatively
different from the case of normal, nonrelativistic electrons. Massless Dirac
fermions in graphene allow a close realization of Klein's gedanken experiment
whereas massive chiral fermions in bilayer graphene offer an interesting
complementary system that elucidates the basic physics involved.Comment: 15 pages, 4 figure
Modeling electromagnetic form factors of light and heavy pseudoscalar mesons
The electromagnetic form factors of light and heavy pseudoscalar mesons are
calculated within two covariant constituent-quark models, a light-front and a
dispersion relation approach. We investigate the details and physical origins
of the model dependence of various hadronic observables: the weak decay
constant, the charge radius and the elastic electromagnetic form factor.Comment: 6 pages, 4 figures, use revtex4. Figure 2 and references are
corrected. Acknoledgments are adde
Spectral Density Functional Approach to Electronic Correlations and Magnetism in Crystals
A novel approach to electronic correlations and magnetism of crystals based
on realistic electronic structure calculations is reviewed. In its simplest
form it is a combination of the ``local density approximation'' (LDA) and the
dynamical mean field theory (DMFT) approaches. Using numerically exact QMC
solution to the effective DMFT multi-orbital quantum-impurity problem, a
successful description of electronic structure and finite temperature magnetism
of transition metals has been achieved. We discuss a simplified perturbation
LDA+DMFT scheme which combines the T-matrix and fluctuation-exchange
approximation (TM-FLEX). We end with a discussion of cluster generalization of
the non-local DMFT scheme and its applications to the magnetism and
superconductivity of high-Tc superconductors.Comment: 37 pages, to be published in: "Electron Correlations and Materials
Properties 2" ed. by A. Gonis (Kluwer, NY
The most incompressible metal osmium at static pressures above 750 gigapascals
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